This application claims priority to Korean Application No. 10-2001-0015449 filed Mar. 24, 2001 entitled Toner Composition for Organic Black matrix and Preparation Method Thereof.
1. Field of the Invention
The present invention relates to a toner composition for an organic black matrix and a preparation method thereof for realizing color pixels of a liquid crystal display device.
More particularly, the present invention relates to the use of a toner composition, prepared by mixing a block copolymer resin having a high molecular weight and containing a pigment affinity group such as a hydroxyl group, a carboxyl group or an amine group and carbon black as a medium with a solvent and a dispersion adjuvant, in the manufacture of an organic black matrix as a component of the color filter of LCD, thereby enhancing the electrical properties, color and chemical resistance of the organic black matrix.
2. Background of the Related Art
Generally, the substrate of a color filter is manufactured by a known method including dyeing, pigment dispersion or electrodeposition. In particular, the black matrix is usually fabricated by the pigment dispersion method.
The pigment dispersion method is a method of manufacturing a color filter that repeatedly comprises the steps of coating a photosynthetic composition containing a colorant on a transparent substrate of the black matrix, performing an exposure of a desired pattern, removing the unexposed portions with a solvent, and performing a heat curing. The pigment dispersion method, which enhances the most important characteristics of the color filter, i.e. heat resistance and durability and maintains the thickness of the film uniform, is most widely used in the preparation of the black matrix. For example, Japanese patent publication No. 63-309916, Japanese patent publication No. 1-152449 and Korean patent publication No. 95-3135 disclose the preparation methods of black matrix using pigment dispersion. The black matrix prepared by the pigment dispersion method is largely composed of a polymer, i.e. a binder resin for supporting the black matrix and maintaining the thickness of the black matrix uniform, and a photopolymerizing monomer reactive to light during the exposure to form a photoresist phase. The black matrix may additionally comprise a photosensitive resin composition including pigment, polymerization initiator, epoxy resin, solvent, and other additives.
Solid fine particles such as pigments represented by carbon black, magnetic powder or ceramic powder are preferably not used alone but in combination with various compositions of different concentrations in order to provide various functions of coloring, reinforcement, tamping or chemical resistance.
Until now, there has been known a method using chrome monolayer, chrome/chrome oxide bilayer, organic matrix, graphite or manganese dioxide as the material of the black matrix. The most general material of the black matrix is sputtered chrome rather than spin-coated organic polymers. In spite of vacuum evaporization or other coating techniques for nickel and aluminum or even chrome, the sputtered chrome is still the most popular material of the black matrix. However, these techniques and materials do not meet the requirements for properties such as resistivity and optical density (O.D.) in the range of thickness less than 1 xcexcm and therefore have limitations in their usage.
Dispersing equipment used in the pigment dispersion method may be those using a medium (e.g., glass beads or zirconium beads), such as 3-roll mill, sand mill, eiger mill, spike mill, dyno mill, Boa mill. Pigment dispersion with a ball mill or the like has difficulty in uniformly coating the whole surface of the solid fine particles with a polymer graft at a low mixing ratio of the reactive polymer to the solid fine particles, in which case the resulting surface-modified particles have a low content of the solid fine particles only to reduce the necessary characteristics of the solid fine particles. The above-mentioned dispersion methods have been used in the preparation of paints, inks or plastics and caused problems such as metal powder, bead abrasion and external contamination.
It has been considered that the organic black matrix having an O.D. of greater than 2.0 is almost impossible to prepare with the thickness of the superthin black matrix (less than 1 xcexcm). With the progress of carbon black processing and dispersion techniques, a dispersing resin, a solvent and an additive are admixed under optimized dispersion conditions and the mixture is dispersed with dispersion facilities using a completely opposing impact method in the center of the dispersion chamber under a high pressure condition rather than by a conventional dispersion system using a medium such as glass bead or zirconium bead. This new method allows dispersion of the pigment to the primary particle size of the carbon black, that is, the particle size of the pigment basically formed in the preparation of the pigment, thereby increasing the O.D. value, enhancing storability and reducing the problematic contamination of the material of the electronic parts using the conventional medium dispersion system.
Though the dispersion method based on the Brownian motion through the medium such as glass bead or zirconium bead is the most popular method used in the related art, it has difficulty in preparing a toner composition having a superthin (less than 1 xcexcm) organic black matrix with a O.D. of greater than 2.0 and causes contaminations due to the abrasion of the chamber. Thus there is a need for a novel dispersion method.
Accordingly, the present invention is directed to a toner composition for an organic black matrix and a preparation method thereof that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an environment-friendly toner composition for an organic black matrix of a color filter that is stable in storage and superior to the conventional toner composition in light resistance, color permeability, particle size distribution, coatability and pattern uniformity, and a preparation method thereof.
Another object of the present invention is to provide a novel dispersion method for preparing an organic black matrix of a color filter by dispersing the toner composition onto a substrate under high pressure.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof.